kui-derive

#[derive(Message)] for kui: a Rust enum or struct to and from the plain-data payload a kui message is.

kui carries every message as a Value map shaped {kind, ...fields}, so one view model serves Rust, Lua, C and Node alike. This derive lets a Rust app keep a typed enum instead: widgets::button(ui, "Save", Msg::Save) sends it and ev.message::<Msg>() reads it back. Most apps get the derive through kui-native (use kui_native::Message; cargo feature derive, on by default) and never name this crate.

Install

cargo add kui-native

Only a crate that depends on kui-core alone needs this crate directly: cargo add kui-derive, then #[message(crate = "kui_core")] on each type.

Example

use kui_native::widgets;
use kui_native::{App, Message, NodeSpec, Ui, UiEvent};

#[derive(Message, Clone, Debug, PartialEq)]
enum Msg {
    Inc,                          // {kind: "inc"}
    Pick { id: u64 },             // {kind: "pick", id: 3}
    #[message(kind = "add10")]
    AddTen,                       // {kind: "add10"}
}

#[derive(Default)]
struct Counter {
    count: i64,
}

impl App for Counter {
    fn view(&mut self, ui: &mut Ui<'_>) {
        ui.with(NodeSpec::row().gap(8.0), |ui| {
            widgets::button(ui, "+1", Msg::Inc);
            widgets::button(ui, "+10", Msg::AddTen);
        });
    }

    fn on_event(&mut self, ev: UiEvent) {
        match ev.message::<Msg>() {
            Some(Msg::Inc) => self.count += 1,
            Some(Msg::AddTen) => self.count += 10,
            Some(Msg::Pick { id }) => println!("picked {id}"),
            None => {}
        }
    }
}

The derive generates From<Msg> for Value, TryFrom<Value> (with a MessageError naming what did not fit) and MessageField, so a message can be a field of another. #[message(string)] on an enum of unit variants encodes it as a bare string instead of a map.

Where it fits

Documentation

• API: https://docs.rs/kui-derive
• The book: https://kui-book.qxuken.dev
• Repository: https://github.com/qxuken/kui

License

MIT